The present invention generally relates to copying apparatuses and more particularly, to an automatic duplex copying type copying apparatus equipped with an automatic document feeder (ADF) for automatically feeding original documents onto an original platform sheet by sheet, in which opposite copying faces of each original document fed from the automatic document feeder are automatically copied onto corresponding opposite faces of each copy paper sheet, respectively.
Conventionally, in duplex copying type copying apparatuses each equipped with an automatic document feeder, it has been generally so arranged that in the case where opposite copying faces of each original document are, respectively, copied onto opposite faces of each copy paper sheet, an original document having opposite copying faces is transported to a turnover unit upon completion of copying of one copying face of the original document onto one face of a copy paper sheet so as to be turned over by the turnover unit and then, is returned to an exposure position once again so as to be copied, at the other copying face, onto the other face of the copy paper sheet such that, upon completion of copying of the opposite copying faces of the original document onto the opposite faces of the copy paper sheet, the next copy paper sheet having opposite copying faces is fed to the copying apparatus.
Therefore, the known duplex copying type copying apparatuses have such a disadvantage that since turnover of the original document upon copying of one copying face of the original document onto one face of the copy paper sheet causes loss of time, a long time is required for copying the opposite copying faces of the original document onto the opposite faces of the copy paper sheets as compared with the case in which the original documents each having one copying face are copied onto opposite faces of the copy paper sheets. Especially, the known duplex copying type copying apparatuses have such a drawback that an extremely long time period is required for copying original documents of large size such as A3, etc.
Meanwhile, in accordance with the recent trend towards diversification of functions for improvement of commercial values, there has been proposed an automatic duplex copying type copying apparatus as shown in FIG. 1. In FIG. 1, an automatic document feeder (ADF) 67 is provided on an original platform of an apparatus housing 51. A sorter 59 is mounted in the vicinity of a copy outlet, on the apparatus housing 51. In the case where copying faces of two original documents are copied onto opposite faces of each copy paper sheet respectively by the prior art copying apparatus of the above described arrangement, a first originial document having a copying face to be copied onto a front face of each copy paper sheet is fed onto the original platform from one of original feeding trays 69 and 70 mounted on the automatic document feeder 67. Subsequently, although not specifically shown, upon actuation of a print switch of an operating portion, a copy paper sheet is fed, synchronously with the scanning of an optical system and rotation of a photosensitive drum 52, from one of paper feeding cassettes 53a and 53b and a manual paper feeding tray 54 mounted on a paper feeding portion. The copy paper sheet is passed between the photosensitive drum 52 and a transfer charger 55 and then, between the photosensitive drum 52 and a charge eraser such that the copying face of the original document is copied onto a front face of the copy paper sheet. Then, the copy paper sheet is temporarily guided into the sorter 59 by a transport belt 57 and a pair of outlet rollers 58. Thereafter, the transport direction of the copy paper sheet is reversed through rotation of a transport belt 61 and a pair of turnover rollers 62 so as to be stored in an intermediate storage tray 64 by two pairs of inlet rollers 63. The copying face of the first original document is continuously copied onto a front face of each of a preset number of copy paper sheets such that the present number of copy paper sheets, each having the front face copied from the copying face of the first original document, are stored in the intermediate storage tray 64. After the copying face of the first original document has been copied onto the front face of each of the preset number of the copy paper sheets, a second original document having a copying face to be copied onto a rear face of each copy paper sheet is fed onto the original platform from the other one of the original feeding trays 69 and 70 of the automatic document feeder 67.
Subsequently, upon actuation of the print switch, a paper feeding roller 65 and a pair of transport rollers 56 are rotated synchronously with scanning of the optical system and rotation of the photosensitive drum 52. Therefore, the copy paper sheets, each having the front face copied from the copying face of the first original document and the rear face confronting the photosensitive drum 52 are passed between the photosensitive drum 52 and the transfer charger 55 and then, between the photosensitive drum 52 and the charge eraser from the intermediate storage tray 64 so as to be copied, at the rear face, from the copying face of the second original document. Thus, the copy paper sheets each having the front and rear faces copied from the copying faces of the first and second original documents, are guided respectively into the sorter 59 by the transport belt 57 and a pair of the outlet rollers 58 and then, are respectively ejected onto corresponding ones of bins 68 provided in the sorter 59 through rotation of a pair of inlet rollers 60 and the transport belt 61, whereby the copying faces of the first and second original documents have been respectively, copied onto the front and rear faces of each of the preset number of copy paper sheets.
In the prior art copying apparatus of FIG. 1, the original document is ejected onto an original outlet portion immediately after completion of copying of the original document. Thus, the prior art copying apparatus is disadvantageous in that if jamming of the copy paper sheets, each having the front face copied from the copying face of the first original document, takes place during transport of the copy paper sheets in the course of the duplex copying, resulting in the requirement that an insufficient number of the copy paper sheets should be copied again, the first and second original documents are required to be manually placed on the original feeding trays, respectively, such that the copying faces of the first and second original documents confront the original feeding trays, respectively, thereby hampering the automatic copying operation.